The reality of Vista is that, even though it sucks, does it matter? All operating systems suck. Vista sucks more than XP and MacOS X and less than say, Windows Me and MacOS 9. But since all OSes suckj, the reality is it doesn't make that big of a difference in your day to day life whether you use Vista or XP.
That doesn't mean that Microsoft doesn't have a big problem on their hands. The hatred of Vista leaves an opening for competition to move in and sell a lot of units.
What Microsoft has to do is look at what Intel did a few years ago.
The Pentium 4 was a hugely flawed chip. Intel shipped millions of them, they made a lot of money, sure. But they knew that the Pentium 4 was flawed very early in its life. So while they were selling Pentium 4s, they scrapped plans to try and build on that architecture and instead went back to the last architecture (Pentium 3/Pentium M) and started from that.
Microsoft should do the exact same thing with Vista. They'll ship millions of copies. Don't be fooled into thinking that this is because the public really likes your product. The only reason people bought Vista is because it's what their $599 Dell came with (usually) . So take a long hard look in the mirror: all operating systems suck, and Vista happens to suck more than the last Windows version.
What's the fastest way out of this problem?
Basically, go back to XP. Rework the UI a little bit, and throw out most of the crap you've messed up with Vista. Drop the insane shutdown menu that took months to develop and is still more complicated than XP. In fact, drop everything except stuff that can easily be installed on top of XP, e.g. WPF, .NET 3.5, etc. If you want to add features to the Windows Explorer, keep the ideas that worked (the Windows-key search box) and drop the things that didn't (Aero glass, the new networking menus, the new save as box, the new path browser at the top of windows.).
And bring back hardware accelerated GDI+ drawing... oh wait, XP has that.
This was done really well, it's a tongue in cheek review of Microsoft's "new" OS, Windows XP, and how great it is to upgrade from Vista.